The present invention is directed to a method and apparatus for processing semiconductor wafers.
A phenomenon which can reduce the yield of useful die from wafers during a semiconductor wafer processing step is the occurrence of arcing, also known as microarcing. Generally, during wafer processing, arcing can occur across the semiconductor wafer and in particular can be concentrated at material defects such as a crack, or at prominent feature of the wafer, which has been processed into the wafer, such as for example pillars. When such arcing occurs, part or all of the wafer can be irreparably damaged.
The present invention is directed to minimizing or eliminating arcing across a semiconductor wafer during a semiconductor wafer processing.
The invention describes a methodology and apparatus used to eliminate and/or substantially decrease the arcing or dielectric breakdown which may occur on a semiconductor wafer or substrate. The invention includes using a chuck and preferably an electrostatic chuck to control the electrostatic clamp voltage applied to the wafer to within a suitable range of values, such that arcing or dielectric breakdown is substantially reduced or eliminated. Such controlling can occur dynamically as process values change during the process steps. Further, by way of example only, such invention is of particular value with wafers containing film having a high dielectric constant or wafers containing films of ferroelectric material. However, such invention is useful for etching all types of standard and conventional films where arcing can also be a problem.
In particular, the apparatus and method are particularly useful for reducing or eliminating arcing or dielectric breakdown during etching in a plasma reactor.
Further, the invention includes a reactor for processing a semiconductor wafer which includes a reactor chamber and a chuck, and preferably an electrostatic chuck, which can accept a wafer for processing. The reactor includes a power supply associated with the reactor chamber, which the power supply is capable of generating a first voltage at the surface of the wafer adjacent to the plasma during the processing of the wafer. The invention further includes a control mechanism that can control a second voltage that the electrostatic chuck applies to the wafer in order to hold the wafer to the chuck during wafer processing. The control mechanism is capable of adjusting the second voltage so that the difference between the first voltage and the second voltage or, in other words, the potential across the wafer, is kept below a threshold in order to minimize arcing across the wafer. Such adjustments can be made dynamically, if desired throughout the wafer fabrication process.
Accordingly, one aspect of the invention includes apparatus that controls the voltage applied to the surface of a wafer in contact with an electrostatic chuck in order to minimize the difference between the applied clamping voltage and the voltage built up on the other side of the wafer which is in contact with, for example, a plasma generated in an etch reactor.
A method of the invention includes the steps of placing a semiconductor wafer into a reactor and onto an electrostatic chuck, and generating a plasma in the reactor. The method further includes controlling the voltage across the wafer in order to minimize arcing.
In an aspect of the invention, the controlling step includes controlling the difference between the voltage at the first surface of the wafer in contact with the plasma, and the voltage at a second surface of the wafer in contact with the chuck.
In another aspect of the present invention, the plasma is generated by at least one of a high frequency power supply and a low frequency power supply.
In a further aspect of the present invention, both the high frequency power supply and a low frequency power supply are applied to the chuck.
In a further aspect of the present invention, the method includes applying a semiconductor processing step to one of high dielectric constant film on a substrate and a ferroelectric film on a substrate.
Accordingly, it can be seen that the present invention is effective in reducing or eliminating arcing across a wafer and in particular a wafer which has a high dielectric constant film and/or ferroelectric film. Such invention is advantageous in that it increases the yield of die.